Die set leader pins and leader pin bushings



July 31, 1956 K. JANlszEwsKl 2,756,825

DIE SET LEADER PINS AND LEADER PIN BUSHINGS Filed Dec. 2l. 1951 2Sheets-Sheet l July 31, 1956 K. JANlszEwsKl DIE SET LEADER PINS ANDLEADER PIN BUSHINGS 2 Sheets-Sheet 2 Filed Dec. 2l, 1951 United StatesqPat-ern:

DIE SET LEADER rINs AND LEADER PIN BUSHINGS Kasimir Janiszewski, HalesCorners, Wis. Application December 21, 1951, Serial No. V262,815 Claims.(Cl. 164-;1'1'8) This invention relates to improvements in die setleader '.'pins and l*leader pin bushings having clearances variable inthe course of their relative movement.

One of the objects of the invention is to facilitate separation of theplatens of a die set without cramping the leader pins in theirrespective bushings. For this purpose, leader pin and bushing assemblieshaving variable 'clearance between the respective leader pins andbushings are provided.

The problem of die set leader .pins `cramping in their 'punch holderbushings is particularly noteworthy whenever the punch holder of the dieset is removed for punch changing or other purposes. The punch holder isconventionally guided by a plurality of leader pins, varying'in number,but frequently four, one at each corner of the punch holder. As thepunch holder is lifted from the die set, by a crane or the like, it may,'as it is about to clear the top ends of the leader pins, tilt or cantto withdraw completely-from one pin before clearing the 'remaining pins,and thus cramp or seize and even bend the other leader pins, or break orcrack 'the bushings. Even if the punch holder does not prematurely clearone pin, the gradual reduction in bearing surface 'may permit the ,punchholder to tilt and 'cramp or bend one or all 'of the pins.

Accordingly, it is one object of the present invention to obviate thisdiiculty by providing the leader pins with immediately availableclearance during the course of vplaten separation either between thebushings and the leader pins, or between the leader pin cores yandseparable sleeve portions thereof, or both, thereby eliminating the,possibility of cramping.

Another important object of the invention Vis to provide leader pins andbushings having variable clearance to -slidably engage with precision tonly during that critical portion of the punch holder stroke when thepunch is engaging the work, and are relatively yfree of close contactduring other and less critical portions of the punch holder stroke.

Forthese purposes a leader pin and'bushing sleeve assembly is providedwith complementary mating surfaces which provide close guidance ataxially remote points but afford increased clearance immediately as Itheplatens separate. In preferred embodiments of the i`nvention, thetapered surfaces comprise stepped cylindrical surfaces rather thansurfaces of 'frusto-.conical form. In all embodiments, however, theleader pin and bushing sleeve have complementary surfaces which haveclearance progressively increasing in the direction of withdrawal of'the punch holder from the die shoe and decreasing in the direction ofwork engagement.

A specific object is to provide, in V'one vembodiment of the invention,a sectional leader pin having internally tapered complementary-'cored'and socketed sections with coupling means therebetween.

Other objects and advantages of the invention will be 'more apparent toone skilled in the art upon an exarn'iiiation Yof the followingdisclosure.

2,756,825 Patented July 31, 1956 In the drawings:

Fig. 1 is a'p'erspective view of a die set having separable platens andleader pin and bushing sleeve assemblies embodying the invention.

Fig. 2 is an enlarged vertical cross section through a portion of thedie set and one embodiment of a sectional leader pin and bushing sleeveassembly, portions of the leader pin being shown in elevation and otherportions being shown in section to expose details of construction.

Fig. 3 is an aXial cross section through the leader pin only of Fig. 2,ythe respective leader pin sections being shown in separated position.

Fig. 4 is a view partly in elevation and partly in cross section of amodiiication of the sectional leader pin shown in Figs. 2 and'3.

Fig. 5 is a lfragmentary view of a still further modification of asectional 'leader pin embodying the invention.

Fig. 6 4is a vertical cross section through a portion of a die sethaving a leader pin and bushing Vsleeve assembly with ycomplementarystepped cylindrical bearing surfaces, the leader pin being shown inelevation.

Fig. 7 is a view similar to that of Fig. 6 showing a modieation in thelbushing sleeve.

Fig. 8 is a further modification ofthe device ofV Fig. 6.

Fig. 9 shows a modification of the device of Fig. 2, showing a`different form of sectional leader pin.

Fig. ll0 is a different aXial cross sectional view of the device-of Fig.9, showing 'the respective leader pin -sections in the course ofseparation.

Fig. /ll is a cross sectionalvview through a modied form yof the deviceshown in Fig. 9.

Fig. 12 is a vertical cross section 4through a portion of a die setfitted with a vmodified form of a tapered leader pin and bushingembodying -the invention.

Fig. 13 'is a cross sectional View Vtaken along the lines 13-13 of Fig.12.

A die set having separable platens comprising a die shoe 20 and punchholder 21 is diagrammatically shown in Fig. l. As best indicated in Fig.2, the die shoe normally carries Ia die, illustrated diagrammatically'at 22, and has at least i-one upstanding leader pin 2S. The punchholder carries a punch, illustrated diagrammatically at 23, Vand isprovided with a bushing in which the leader pin is slidable 'to guidethe punch as it reciprocates with the punch holder to coact with the die22 upon the work 'illustrated diagrammatically at 24.

Individual leader pin assemblies, usually two, three 'or four in number,are normally provided at each corner of the die set, as best shown inFig. l. Prior to the present invention, the respective leader pins andpunch holder bushings were made with complementary precision fittedbearing-surfaces extending for substantially the full height of thepunch holder and full length of the leader pins.

The improved leader pin and bushing assemblies yillustrated in theaccompanying drawings, and which are hereinafter described, all arestructurally designed to provide for lateral clear-ance between theleader pin and bushing when the punch holder is -separated from the dieshoe. Several embodiments of leader pin and bushing taper will behereinafter described. Some of these embodiments comprise complementaryfrus'to-conical mating surfaces, and other embodiments comprise steppedcomplementary cylindrical surfaces. I choose' to denominate theconfiguration of thesevar'ious modifications by a generic term taper,and such term will be understood as used throughout the specication andclaims, except as otherwise indicated, to mean compl'ernentary matingsurfaces of progressively smaller diameter in the direction 4of punchholder Withdrawal. A

In 'the preferred construction shown in Figs. 2 and 3, a sectionalleader pin having-acore section l2-5 is provided with la head l26 havingdiscontinuous upwardly `tapered 3 frusto-conical surfaces 27 and 28.Sleeve section 31 is provided with a cylindrical bore 3.3 and acommunicating tapered bore or inner surface 32 complementary with thehead surfaces 27 and 2S.

At the junction of the cylindrical bore 33 and tapered bore 32, anapertured and countersunk plug 3d is inserted to serve as a seat for thehead of a screw 35 which couples the sleeve section 31 and the coresection 25 of the leader pin. Plug 34 is rotatably keyed to sleeve 31 bymeans of a snap expansion ring 3S which fits within the annular spaceprovided by aligned peripheral grooves 36 and 37 in the plug and sleeve,respectively.

Head 26 of the leader pin section 25 is axially tapped at 41 to receivethe threads of coupling screw 35, the head of which is seated in thecountersunlc aperture 4f?. in the plug 34. The head of screw 35 isprovided with a socket 43 to receive a socket wrench such as the wrenchla shown in Fig. 3. ln order to develop axial thrust between the sleeveand the head. sections to separate these sections,

plug 34- may be shouldered above the head of the screw,

whereby turning the screw in a direction to remove it from tap 41 willexert thrust against the plug to separate the sections. In theembodiment of Figs. 2 and 3, the shoulder is provided by upsettingportion 46 of the plug near its top surface over the counterbore, anapertured washer being first positioned over the screw head and belowthe top surface of the plug.

ln the embodiment of Fig. 5, a welsh plug 43 may be used to provide theshoulder in lieu of upsetting the plug.

Plug 34 is provided, in its counterbore 42, with an under- A cutperipheral groove 47 within which the centrally apertured welsh plug 48may be driven to substitute for the washer 4S of Figs. 2 and 3 and toprovide the shoulder against which the head of the bolt 35 acts. Thefunction of the shoulder is best illustrated in Fig. 3, where the isleeve section 31 has been partially lifted from the core section 26,thus laterally as well as axially clearing the complementary taperedfrusto-conical surfaces 32 and 27, 28.

A somewhat modified form of the sectional leader pin is shown in Fig. 4wherein the sleeve 51 of the sectional leader pin is internally threadedat 52, and is provided with a plug 53 complementarily threaded at 54.The threads hold the parts together, as compared to the snap ringarrangement of the embodiments of Figs. 2 and 3. ln the embodiment ofFig. 4, however, plug 53 may be advanced axially on its threads towardthe top of the leader pin core 55. Upon contact of the downwardlyprojecting boss 56 of the plug with the core top, axial thrust isdeveloped to separate the sleeve and core sections.

By reason of the threaded connection of the sleeve section 51 and plug53, the coupling screw 57 need not be used to separate these parts.Accordingly, the plug counterbore 5b is smooth-walled and not providedwith a shoulder. The plug 53 is, however, provided with sockets 59 toreceive a wrench to turn the plug respecting the sleeve section 51.

A still further sectional leader pin modification is shown in Figs. 9,l0 and ll wherein the leader pin comprises an anchorage section 61having a head 62 with a continuous frusto-conical tapered surface 63mating with the cornplementary frusto-conical tapered bored surface 64of sleeve section 65 of the pin. Sleeve section 65 has an integrallyformed transverse web 66, as distinguished from .A

the separate plug 34 in the embodiment of Fig. 2, and which constitutesthe base of the socket 64. Web 66 is provided with a central aperture 67and a counterbore 72 through which a screw 68 extends to threadedengagement with tap 71 of core 62. Counterbore 72 is threaded at '73 fora purpose to be hereinafter described in more detail.

Screw 68 has a socketed head 74, of less outer diameter than the webcounterbore 72. Accordingly, axial movement and rotation of the head 74is not interfered with by l the thread 73. Screw 68 serves to couple thecomplementary tapered socketed and cored sections of the lleader pin. Atransverse aligning pin 75 may be provided at the junction of thesocketed and cored leader pin sections to assure uniform registration ofthe sectional parts.

At such times as it is desired to clear the socketed and cored sectionsof the leader pin, as incident to withdrawal of the punch holder 21 fromthe die shoe 20, screw 68 may be removed and replaced by a jack stud 76(Fig. l0) having an enlarged head 77 with threads '73 engaging thethreads 73 of the counterbore 72. Head 77 is provided with a centralsocket 31 to receive a soclret Wrench 82 whereby separating thrust maybe developed between the threads 73 in the socketed section 65 of theleader pin and the cored section 61 of the leader pin through theunthreaded jack stud 76. As clearly shown in Fig. 10, separation of themating leader pin sections will result in lateral as well as axialclearance between the frusto-conical surface 63 on the core 62, and themating frusto-conical surface 64 on the socketed section 65 of leaderpin.

if, during use of a die set, the leader pin section 65 seizes in bushing91, the screw 68 will break to permit leader pin section 61 to withdraw,with constantly increasing clearance, from the tapered socket in section65, thus precluding damage. Screws 35, 57 and 88 may be frangible forthe same purpose.

A somewhat moditied form of the device shown in Figs. 9 and lO is shownin Fig. ll. In this modification, the head section 83 of the leader pinis provided with a smooth wall counterbore S4 having an internallyfacing groove 35 near its top end to receive a snap ring 86 whichprovides an upper shoulder against which the socketed head S7 of screwS8 may act. In this manner the same screw 88 accomplishes the functionof the threaded screw 63 in Fig. 9 and the jack screw 76 in Fig. 10.

In the embodiments of the invention shown in Figs. 9, l0 and 1l, thepunch holder 21 is provided with a conventional continuouslycylindrically walled bushing 91 complementary with the cylindrical outerwall or surface 92 of the socketed portion of the sectional leader pin.Accordingly in these embodiments the leader pin and bushing are inbearing relation throughout the normal range of such holderreciprocation.

In the embodiment of Fig. 2, however, provision is made to permit theleader pin to ride free in the bushing except at the critical point inthe stroke where the dies coact upon the Work. The punch holder bushingcomprises axially spaced cylindrically walled collars 93 and 94, thecollar 93 having an inner cylindrical surface 95 of smaller diameterthan the inner cylindrical surface 96 of the collar 94. A spacer 97, ofgreater internal diameter than the collars, separates the collars 93 and94. An external washer 98, of still greater internal diameter, holds thecollars and spacer assembled against the annular shoulder 99 of thepunch holder. The washer 9S is held against the under surface of thepunch holder 2.1 and against the under surface of the collar 94 by oneor more screws 101. The external surface of the socketed portion 31 ofthe leader pin is stepped to provide cylindrical surfaces 102 and 103,said surfaces being complementary with the cylindrical surfaces and 96of collars 93 and 94, respectively.

By reason of the spacing of collars 93 and 94, bearing engagement oftheir inner surfaces 95 and 96 with leader pin surfaces 102, 103 occursin only a short range of punch holder reciprocation. The leader pin 25is so positioned in die shoe Ztl that these bearing surfaces do not comeinto engagement until the dies are about to coact upon the work.yAccordingly, the leader pin acts as a guide only during the short periodof the stroke of the punch holder when accurate guiding is of utmostimportance. At all other times, th punch holder is relatively free andclear of Vthe leader pin. Inthis manner l cylindrical bushing sleevesurfaces.

of Fig. 6, the bushing bearing surfaces comprise the bottom collar 125seats.

lshoulder l128.

aduanas wear on the pin and bushing .is greatly reduced and'crfamp- .ingbecomes virtually impossible because Vthe Icomple- -mentary bearingsurfaces at opposite endsof the leader 4pin clear simultaneously inresponse to the lirstwithdrawal movement.

In the embodiments of the invention shown in Pigs. 6 and 7 the leaderpin is a vone piece construction, the conical tapers and screw beingomitted. Instead, `the upward taper on the leader pin 104 is in the formo'fstepped cylindrical surfaces 105, 106 and 107, the respectivesurfaces being of .progressively smaller diameter in the direction of-punch holder Withdrawal. These stepped vleader pins surfaces4 mate withcomplementary stepped In the -embodiment stepped surfaces 10S, 109.,110. These surfaces are inwardly embossed on common sleeve 113: toprogressively .smaller diameters in the ldirection of `punch holderWithdrawal. Common sleeve 1.13 ris further provided with an outturnedbottom flange 114 which abuts the bottom surface of the punch holder l21to position the sleeve respecting the punch holder. Sleeve 113 is.norm-allyheld .within the punch holder aperture 11.2 by a press it.

In the embodiment of Fig. 7, the stepped complevmentary cylindricalbushing surfaces 115, 1.16 and )117 comprise the vinner annularperipheries of raxially .spaced Acollars or rings which are separatefrom, but .axially .spaced by, spacer sleeves 118 and 119. The sleevesand collars are held in assembly against the shoulder r120 "of the punchvholder by an annular washer 121, similar to washer 98 in Fig. 2.

vIn either of the embodiments of Figs. -6 and 7, the bearing surfaces ofthev punch holder bushing .or sleeve comprising the respective collars4or embossmen'ts .are substantially spaced axially. The lleader .pin isalso .so positioned that these bearing surfaces do not contact theleader pin surface until near the end of the downward stroke of thepunch holder. Accordingly, :almost immediate lateral, as well as axial,disengagement -of the leader .pin cylindrical bearing surfaces from thepunch `holder bushing or sleeve cylindrical.bearingvrsurfaces will occurafter upward movement Ao'f the punch vholder has been initiated. In thismanner, lateral clearance between the .leader pin and .punchholderbushing is developed by reason of the stepped complementary.

surfaces and smooth withdrawal of the Apunch holder Vfrom the die shoeWithout cramping or seizing of the bushing against the leader pin isfacilitated.

The embodiments of Figs. 6-and 7 are also characterized by cam actionbetween the respective bearing surfaces on .the punch holder bushing andleader pin during the portions of punch stroke when leader pin.guidanceis most necessary. At all other times, the leader pin is freeandl clear of bearing contact with the punch holder bushing.

In the embodiment yof Fig.. 8, the vleader pin v.124 is pro- .i

vided with stepped cylindrical surfaces of different diameters whichcomprise axially spaced 'annu'l'ar collars 125 and 126 which are slippedover 'a central core `127 of the leader pin. The leader pin is 'providedat 'thelower base of the core 127 with a shoulder'1'28 againstwhichtheSpacer sleeve 129 axially separates the respective collars 125 and1'2'6. Top wa'sherlor ,plate 132, held to the leader pin by 'screwl133', holds the collars fand spacer in unitary assembly against the Inthis embodiment, the punch lholder bushing also comprises axially spacedcollars 13'4 and 135 having stepped cylindrical surfaces`complernenta'ry'with the stepped cylindrical surfaces of the leader pincollars 125 and 126. Collars 134 and 135 are axially spaced by thespacer 136. The respective collars 134 and 135 and spacer 136 are heldagainst punch holder shoulder 137 by means of an external washer 138,which bears against the under surface of the punch holder 21.

As in the embodiments of Figs. 6 and 7, the Fig. 8 embodiment comprisesleader pin and punch holder bearfno -positions'other :than the immediateproximity to .itsrlower- `most position -of the punchholder.. 4Asaforesaid, this Vrelation of lparts prevents punch -holder cramping andlprovides cam act-ion only when accurate leader -,pin guidancet.isrequired In allappropriate embodimentsyby formi-ng the respectivebearing surfaces on removable collars, :as distinguished from forming'them integrally with the bushing sleeve for .leader pinl propenrreadyreplacement -of individual worn collars is made possible, thus reducingmaintenance costs.

.'In the embodiment of the-:invention Ashown inFigs. l2 .and i3, theleader pin 1-41 is provided-with an upwardly frusto-conical taperingsurface 142, and the punch holder bushing 143vis provided withfacomplementary vtapering bore 144. Accordingly, .movement of -"the `punchholder .21 from the die set 'will cl'ea'r thepunchn'holder bushing andmating leader .pin surfaces .in the :manner y'aforesaid :to preventseizing. -.=As :the "tapers mate ronly lat one point in .punch 'holderstroke this arrangement of parts precisely valigns the punch holder 'anddie .shoe lat the bottom ofthe `punch .holderstroke when .Iac'curacy fisdesired, but' permit the `leader pinto separate from -its punch holderbushing at all other times.

:Inorder to adjust the moment at which the fcomple- :mentary tapersmate, in'accordance with theeheight of the 'work .inthe die shoe, the:leader pin :in the embodiment Vof Figs. `l2 and .i3 fprovided "with aclamp mounting in -which the pin is vertically. adjustable.

Theaclamp mounting @comprises a sleeve 145 'Smoun'ted .in the 'punchholder bore 140: The sleeve '145 :is .split along yone side margin at146and isprovidedfwith-an encircling @collar 147 having a clampzarrangementcomprising a nut 148 and bolt 149. The rdiarnet'er of 7thesleeve 145 may thus tbe fchanged whereby to act as aclamp .for theieaderpin 141. In this manner l'ead'er'pin 1-41 may be raised or-lowered inits mounting, and Vtheheight v'of the ,'pin .adjusted so that the.taperron its upper surface will fmatewith thepunchl holder Vbush-ingvtaper fat the precisemoment that the punch `is -at its lowermostposition in its stroke. In the other embodiment k.of the invention, th'evleader pin 'need not be adjustably langle .of the tapered :sides withthe .leader -pin axis is thus vthree f degrees, .thirty-four minutes,yand thirtyve seconds; the included yangle l:of `:the .tapered .sideslbeing seven -de- Vgrecs, nine vminutes and -ten seconds. Such yanangular relationship will y.permit th'e vrespective ifrusto-corrioaltapered parts to adhere under -all normal circumstances but ttoseparateea'isily lupon the exertion of v axial thrust -between the matedparts. While other tapers would provide satisfactory clearances uponwithdrawal .of the punch holder,-the`stated taper is .preferred because7of .its particular -aforenoted characteristic.

.Pro-m the foregoing description, ytaken .in` connection v'with ftheaccompanying drawings,.it is ,clear that 4a novel form of leader gpinfand punch .holder bushing having complementary tapered'surfaees, .whichmay either :be of :truste-conical or of .stepped cylindrical .form,fhas.been provided whereby .later-al as well as axial clearance between the,partsfisf-developed .upon separation. thereof. The particularstructures of the devices .shownuinfFigsr-Z, 3., 4, "6, 7, 8, l2 and 13also provide for cam action of the leader pin bearing surfaces with thepunch holder bushing bearing surfaces in a narrow range of punch holdermovement.

I claim:

1. In a die set having separable platens, the combination with a leaderpin fixed to one of said platens, of a sleeve movable respecting saidleader pinwith the other of said platens, said pin'and sleeve havingcomplementary mating surfaces which are of slightly smaller diameteradjacent their respective upper ends than adjacent their lower ends,whereby separation of said platens will cause lateral disengagement ofsaid surfaces, the said surfaces being in suicient proximity foreffective pin guidance at all points of pin movement within the sleeveand having close working t throughout said surfaces solely adjacent thepoint of die operation.

2. The combination of claim 1 in which the mating surfaces of the pinand sleeve comprise frusto-conical surfaces.

3. The combination of claim 1 in which the mating surfaces of the pinand sleeve comprise stepped cylindrical surfaces.

4. The combination of claim 1 wherein the sleeve cornprises a bushingfast to said other platen. v

5. The combination of claim l wherein said leader pin comprises amounting part and a separable terminal sleeve part, said parts beingprovided with a coupling uniting said parts during normal leader pinaction, said coupling being disengageable to permit the sleeve part tomove with the said other platen during the course of separation of theplatens, said terminal sleeve and first mentioned sleeve having saidcomplementary surfaces.

6. In a die set having platens movable toward and away from each other,the combination with a leader pin fixed to one of said platens and abearing bushing fixed to the other said platen, said bushing and pinhaving complementary stepped cylindrical bearing surfaces concurrentlyslidably engageable with close tit in the relatively proximate positionof the platens in which the die is operative, and laterally free ofengagement and in loose guiding tit in relatively separated positions ofthe platens.

7. The device of claim 6 wherein the cylindrical surfaces on the bushingare axially spaced.

8. The device of claim 6 wherein the bushing comprises a unitary sleevefitting the punch holder, said sleeve having stepped bearing surfacesembossed inwardly to progressively smaller diameters in the direction ofplaten separation.

9. The device of claim 6 wherein the bushing comprises a plurality ofaxially spaced bearing sleeves extending inwardly to progressivelysmaller diameters in the direction of platen separation andcorresponding to the respective pin diameters, and spacers between saidsleeves.

l0. The device of claim 6 wherein said pin comprises separable sectionsand frangible connecting means.

11. In a die set comprising relatively movable platens having coactingleader pin and bushing means, the combination with a leader pin, of aterminal cap sleeve ernbracing an end portion of the pin and externallyprovided with a bearing surface for bushing engagement, and meansdetachably connecting said sleeve to the pin, whereby the pin may befreed in the event the cap sleeve sticks in the bushing.

12. The device of claim 11 in which the pin and sleeve have mutuallyengaged bearing surfaces relatively smaller in diameter near the end ofthe pin than remote from said end, whereby to give immediate increase inradial clearance upon axial relative movement in a direction of sleeveremoval upon detachment of said connection.

13. The device of claim 11 in which the detachable connecting meanscomprises a screw in the endof the pin, said sleeve having abutment andretainer means spanning the end of the pin in xed connection with thesleeve and engaged by the screw.

' 14. The device of` claim 13 in'which the sleeve has a groove in itsinner periphery and said retainer means comprises a circular membermarginally engaged in the groove and with which the abutment means isfastened to be positioned in the sleeve. y

15. The device of claim 13 in which the screw is headed and is frangiblefor the detachment'of said connection to release the pin from the sleevewhen tension is excessive.

16. The device of claim 13 in which the screw is headed and the abutmentand retainer means comprise a thrust surface overlying the screw head todetach the sleeve and pin positively by effecting relative axialmovement in a releasing direction when the screw is unscrewed from thepin. v

17. The device of claim l1 in which the pin and sleeve have mutuallyengaged bearing surfaces relatively Vsmaller in diameter near the end ofthe pin than remote from said end, whereby to give immediate increase inradial clearancel upon axial relative movement in a direction of sleeveremoval upon detachment of said connection, the bearing surfacesincluding axially spaced portions between Which there is clearancebetween the sleeve and pin.

18. The device of claim 11 in which the pin and sleeve have mutuallyengaged bearing surfaces relatively smaller in diameter near the end ofthe pin than remote from said end, whereby to give immediate increase inradial clearance upon axial relative movement in a direction of sleeveremoval upon detachment vof said connection, the said surfaces beingfrusto-conical.

19. In a die set comprising relatively movable platens having coactingleader pin and bushing means, the combination with a leader pin, of aterminal cap sleeve embracing an end portion of the pin and externallyprovided with a bearing surface for bushing engagement, and meansdetachably connecting said sleeve to the pin, whereby the pin may befreed in the event the cap sleeve sticks in the bushing, together with abushing complementary to the sleeve, the sleeve and bushing havingmating bearing surfaces of slightly smaller diameter at the outer end ofthe sleeve than adjacent the pin to provide a close bushing and sleeve tat both ends of the sleeve during die action and increased radialclearance but effective guidance in relative movement to and from thepoint of die action.

20. The device of claim 19 in which the sleeve and pin also havecomplementary and normally engaged bearing surfaces of smaller diameterat the end of the pin than the diameter remote therefrom to provideincreased radial clearance between the cap sleeve and pin upon relativepin withdrawal consequent upon detachment of said connection.

References Cited in the tile of this patent UNITED STATES PATENTS629,429 Corscaden July 25, 1899 789,021 Hartman May 2, 1905 1,543,010Johnson June 23, 1925 1,875,930 Martin Sept. 6, 1932 2,205,731 OlsenJune 25, 1940 2,236,221 Schwayder Mar. 25, 1941 2,433,617 Marsilius Dec.30, 1947 2,504,642 Burgess Apr. 18, 1950 2,523,358 Conner Sept. 26, 1950Ianiszewslci Sept. 22, 1953

